Disk drives are digital data storage devices which allow host computers to store and retrieve large amounts of data in a fast and efficient manner. A typical disk drive includes a plurality of magnetic recording disks which are mounted to a rotatable hub of a spindle motor and rotated at a high speed. An array of read/write heads is disposed adjacent to data storage surfaces of the disks to transfer data between the disks and a host computer. The heads can be radially positioned over the disks by a rotary actuator and a closed loop servo system, and can fly in close proximity to the surfaces of the disks upon air bearings. The heads each typically contain a separate read element and write element.
Higher data storage density on the disks may be obtained by reading and writing data on narrower tracks on the disks and by maintaining a corresponding smaller flying height gap between the read/write elements and the data storage surfaces. The flying height of a read/write element can vary in response to air density changes in the disk drive, and in response to head temperature variations which can affect the distance that the tip of the head, where the read/write elements are located, protrudes therefrom (i.e., pole-tip protrusion). Some disk drives use a heater to controllably heat the tip of the head in order to vary the flying height of the read/write elements.
Maintaining the head flying height within an acceptable range is becoming increasingly more difficult as that range is reduced to maintain an acceptable bit error rate (BER) when data storage densities are increased. Operation outside the acceptable range may result in an unacceptable read/write BER and/or undesirable contact between a head and a data storage surface and potential loss of data and/or damage to the data storage surface.
The flying height of a read/write element may be affected by the temperature of the head. Accordingly, when estimating/controlling the flying height of the read/write element, it is desirable to estimate/control the temperature of the head. The temperature of the head may be estimated using a temperature estimation model based on the ambient temperature of the disk drive. However, most disk drives have multiple platters and multiple heads per platter. It may be difficult and/or expensive to continuously run estimation models for all of the heads of a disk drive.